Transmitter and control method for transmitting and calibrating a phase signal and an amplitude signal

ABSTRACT

A transmitter for transmitting and calibrating a phase signal and an amplitude signal. The transmitter comprises a phase modulation path, an amplitude modulation path, and a control unit. The phase modulation path transmits the phase signal. The amplitude modulation path transmits the amplitude signal. The control unit delays the signal on at least one of the phase modulation path and the amplitude modulation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of application Ser. No. 12/258,647,filed Oct. 27, 2008, the entirety of which is incorporated by referenceherein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a transmitter and a control method, and moreparticularly to a transmitter and a control method for transmitting andcalibrating a phase signal and an amplitude signal.

2. Description of the Related Art

FIG. 1 is a schematic diagram of a conventional transmitter. Theconventional transmitter 100 comprises mixers 110, 120, a localoscillator (LO) 130, an adder 140, a power amplifier 150, a surfaceacoustic wave (SAW) 160, and an antenna 170. The mixer 110 mixes Idigital baseband data S_(I) with a first carrier provided by the LO 130.The mixer 120 mixes Q digital baseband data S_(Q) with a second carrierprovided by the LO 130. The phase difference of the first carrier andthe second carrier is 90°. The adder 140 adds the mixed signals. Thepower amplifier 150 amplifies the output signal of the adder 140. TheSAW 160 processes the amplified signal and transmits the processedresult via the antenna 170.

BRIEF SUMMARY OF THE INVENTION

Transmitters are provided. An exemplary embodiment of a transmitter,which transmits and calibrates a phase signal and an amplitude signal,comprises a phase modulation path, an amplitude modulation path, acontrol unit, a calibration unit and a digital modulator. The phasemodulation path transmits the phase signal. The amplitude modulationpath transmits the amplitude signal. The control unit delays the signalon at least one of the phase modulation path and the amplitudemodulation path. When the transmitter is in a calibration mode, thecalibration unit is arranged to provide a calibration signal to theamplitude modulation path to serve as the amplitude signal. When thetransmitter is in a normal mode, the digital modulator is arranged toprovide the phase signal and the amplitude signal to the phasemodulation path and the amplitude modulation path, respectively.

Another exemplary embodiment of a transmitter comprises a first filter,a second filter, and a control unit. The first filter generates a phasesignal according to a first signal. The second filter generates anamplitude signal according to a second signal. The control unit delaysat least one of the first and the second signals.

A control method for a transmitter is provided. An exemplary embodimentof a control method for transmitting and calibrating a phase signal andan amplitude signal is described in the following. A phase modulationpath is provided for transmitting the phase signal. An amplitudemodulation path is provided for transmitting the amplitude signal. Thesignal on at least one of the phase modulation path and the amplitudemodulation path is delayed. In a calibration mode, a first calibrationsignal serves as the amplitude signal. In a normal mode, the phasesignal and the amplitude signal are provided by a digital modulator tothe phase modulation path and the amplitude modulation path.

A detailed description is given in the following embodiments withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by referring to the followingdetailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1 is a schematic diagram of a conventional transmitter;

FIG. 2 is a schematic diagram of an exemplary embodiment of atransmitter;

FIG. 3A is a schematic diagram of an exemplary embodiment of thedetection module;

FIG. 3B is a waveform diagram of an exemplary embodiment of the outputsignals of the comparators 321 and 322;

FIG. 3C is a waveform diagram of another exemplary embodiment of theoutput signals of the comparators 321 and 322;

FIG. 3D is a schematic diagram of another exemplary embodiment of thedetection module;

FIG. 4 is a schematic diagram of an exemplary embodiment of a PLL;

FIGS. 5˜7 are schematic diagrams of other exemplary embodiments of thetransmitter; and

FIG. 8 is a flowchart of an exemplary embodiment of a control method.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims.

FIG. 2 is a schematic diagram of an exemplary embodiment of a polartransmitter. The transmitter 200 is capable of transmitting andcalibrating a phase signal Φ(t) and an amplitude signal A(t). In thisembodiment, the transmitter 200 comprises a phase modulation path 210,an amplitude modulation path 220, and a control unit 230. The phasemodulation path 210 transmits the phase signal Φ(t). The amplitudemodulation path 220 transmits the amplitude signal A(t). The controlunit 230 delays the signal on at least one of the phase modulation path210 and the amplitude modulation path 220.

The transmitter 200 further comprises a calibration unit 240 and adigital modulator 250. In a calibration mode, the calibration unit 240provides a calibration signal S_(D1) to the phase modulation path 210and provides a calibration signal S_(D2) to the amplitude modulationpath 220. In this embodiment, the calibration signal S_(D1) is the sameas the calibration signal S_(D2).

Different delays may be introduced on the phase modulation path 210 andthe amplitude modulation path 220, resulting in delay mismatch betweenthe output signals. In the calibration mode, the control unit 230 isutilized to detect the difference of delay between the calibrationsignals S_(D1) and S_(D2) that have passed through the two paths 210 and220. In one embodiment, the control unit 230 adjusts a delay factoraccording to the difference between the calibration signals S_(D1) andS_(D2) such that the signal on at least one of the phase modulation path210 and the amplitude modulation path 220 is delayed. Since delay on atleast one of the phase modulation path 210 and the amplitude modulationpath 220 is compensated, the signals on the phase modulation path 210and the amplitude modulation path 220 are synchronous. When thecalibration signals S_(D1) and S_(D2) are synchronous, the control unit230 stops detecting the difference between the calibration signalsS_(D1) and S_(D2) and maintains the delay factor.

In a normal mode, the digital modulator 250 converts I digital basebanddata 251 and Q digital baseband data 252 into the phase signal Φ(t) andthe amplitude signal A(t). The phase modulation path 210 transmits thephase signal Φ(t). The amplitude modulation path 220 transmits theamplitude signal A(t). Since the delay factor of the control unit 230 isadjusted, the phase signal Φ(t) and the amplitude signal A(t) cansimultaneously arrive to a combiner 260 in the normal mode. The combiner260 combines the phase signal Φ(t) and the amplitude signal A(t) togenerate a radio frequency (RF) signal S_(RF).

The control unit 230 comprises a delay module 231 and a detection module232. In the calibration mode, the detection module 232 detects thedifference of delays between the signals on the phase modulation path210 and the amplitude modulation path 220 and generates an adjustmentsignal S_(ADJ) according to the detection result. When the signals onthe phase modulation path 210 and the amplitude modulation path 220 aresynchronous, the detection module 232 stops detecting the difference andmaintains the adjustment signal S_(ADJ). The delay module 231 delays thesignal on at least one of the phase modulation path 210 and theamplitude modulation path 220 according to the adjustment signalS_(ADJ). In this embodiment, the delay module 231 delays the signal onthe amplitude modulation path 220 according to the adjustment signalS_(ADJ).

Generally, delay is easily introduced by a filter. In this embodiment,the detection module 232 detects the output signal V_(t) of a filter(not shown) disposed on the phase modulation path 210 and the outputsignal V_(L) of a filter (such as 222) disposed on the amplitudemodulation path 220.

FIG. 3A is a schematic diagram of an exemplary embodiment of thedetection module. The detection module 232 comprises differentialgenerators 311, 312, comparators 321, 322, and a flip-flop 331. Thedifferential generator 311 transmits the output signal V_(L) intodifferential signals V_(L+) and V_(L−). The differential generator 312transmits the output signal V_(t) into differential signals V_(t+) andV_(t−). The differential signals V_(L+) and V_(L−) refer to a firstdifferential pair. The differential signals V_(t+) and V_(t−) refer to asecond differential pair. The comparator 321 compares the differentialsignals V_(t+) and V_(t−) and transmits the compared result to theflip-flop 331. The comparator 322 compares the differential signalsV_(L+) and V_(L−) and transmits the compared result to the flip-flop331. The flip-flop 331 generates the adjustment signal S_(ADJ) accordingto the compared results.

In this embodiment, the flip-flop 331 is a D-type flip-flop. The outputsignal of the comparator 321 is transmitted to the input terminal D offlip-flop 331. The output signal of the comparator 322 is transmitted tothe clock terminal CLK of flip-flop 331. When the output signal of thecomparator 322 is changed from a low level to a high level, theadjustment signal S_(ADJ) follows the output signal of the comparator321.

FIG. 3B is a waveform diagram of an exemplary embodiment of the outputsignals of the comparators 321 and 322. The label PM shown in FIG. 3Brepresents the output signal of the comparator 321 and the label AMrepresents the output signal of the comparator 322. When the outputsignal of the comparator 322 is changed from a low level to a highlevel, since the output signal of the comparator 321 is at a high level,the output signal (such as adjustment signal S_(ADJ)) of flip-flop 331is at a high level. Referring to FIG. 3C, when the output signal of thecomparator 322 is changed from the low level to the high level, sincethe output signal of the comparator 321 is at a low level, the outputsignal of flip-flop 331 is at a low level.

FIG. 3D is a schematic diagram of another exemplary embodiment of thedetection module. The detection module 232 comprises voltage generators313 and 314, comparators 321′ and 322′, and a flip-flop 331′. Thevoltage generator 313 receives the output signal V_(t) and generates adivided signal

$\; {\frac{1}{2}{V_{t}.}}$

The comparator 321′ compares the output signal V_(t) and a dividedsignal

$\frac{1}{2}{V_{t}.}$

The divided signal

$\frac{1}{2}V_{t}$

is served as a threshold voltage such that comparator 321′ converts theoutput signal V_(t) from a sine wave to a rectangular wave. The voltagegenerator 314 receives the output signal V_(L) and generates the dividedsignal

$\frac{1}{2}\; {V_{L}.}$

The comparator 322′ compares the output signal V_(L) and the dividedsignal

$\frac{1}{2}{V_{L}.}$

The divided signal

$\frac{1}{2}V_{L}$

is served as a threshold voltage such that comparator 322′ converts theoutput signal V_(L) from a sine wave to a rectangular wave. Theflip-flop 331 generates the adjustment signal S_(ADJ) according to thecompared results of the comparators 321′ and 322′.

In this embodiment, the voltage generator 313 comprises a switch SW6, acapacitor C1, and resistors R1 and R2, but is not limited. The switchSW6 is controlled by a control signal S_(C1) such that the capacitor C1receives the output signal V_(t) or the capacitor C1 is connected to theresistors R1 and R2 in parallel. First, the output signal V_(t) istransmitted to the capacitor C1. Then, the capacitor C1 is connected tothe resistors R1 and R2. Since the resistors R1 and R2 are connected toact as a voltage divider, the divided signal

$\frac{1}{2}V_{t}$

is generated.

Similarly, the voltage generator 314 comprises a switch SW7, a capacitorC2, and resistors R3 and R4, but is not limited. The switch SW7 iscontrolled by a control signal S_(C2) such that the capacitor C2receives the output signal V_(L) or the capacitor C2 is connected to theresistors R3 and R4 in parallel. First, the output signal V_(L) istransmitted to the capacitor C2. Then, the capacitor C2 is connected tothe resistors R3 and R4. Since the resistors R3 and R4 are connected toact as a voltage divider, the divided signal

$\frac{1}{2}V_{L}$

is generated.

Referring to FIG. 2, in the calibration mode, the phase modulation path210 refers to the path from the compensation filter 2112 to the SDM 2121and the PLL 2122. In the normal mode, the phase modulation path 210 canfurther include the differentiator 2111. In this embodiment, thedifferentiator 2111 and the compensation filter 2112 are included in aprocess unit 211. The process unit 211 can enhance certain highfrequency portion of the signal on the phase modulation path 210 by thecompensation filter 2122. In the normal mode, the differentiator 2111differentiates the phase signal Φ(t) and the compensation filter 2112enhances certain high frequency portion of the signal on the phasemodulation path 210. In the calibration mode, the compensation filter2112 enhances certain high frequency portion of the calibration signalS_(D1). In some embodiments, the compensation filter 2112 can beomitted.

In this embodiment, the fractional-N PLL 212 comprises a sigma-deltamodulator (SDM) 2121 and a phase-locked loop (PLL) 2122. The SDM 2121modulates the output signal of the process unit 211 to generate amodulated signal S_(MOD). The PLL 2122 operates according to themodulated signal S_(MOD).

FIG. 4 is a schematic diagram of an exemplary embodiment of a PLL. ThePLL 2122 comprises a phase-frequency detector (PFD) 411, a charge pump(CP) 412, a low pass filter (LPF) 413, a voltage control oscillator(VCO) 414, and a frequency divider (FD) 415. The PFD 411 detects thephase difference between a reference frequency F_(REF) and a feedbackfrequency F_(FB2). The CP 412 transforms the phase difference into apump current I_(CP). The LPF 413 transforms the pump current I_(CP) intothe output signal V_(t). The VCO 414 generates a feedback frequencyF_(FB1) according to the output signal V_(t). The FD 415 divides thefeedback frequency F_(FB1) according to the modulated signal S_(MOD) togenerate the feedback frequency F_(FB2). The detection module 232detects the output signal V_(t) of the LPF 413 to obtain the amount ofdelay of phase modulation path.

Referring to FIG. 2, the amplitude modulation path 220 comprises adigital-to analog converter (DAC) 221 and a filter 222. The DAC 221transforms the signal on the amplitude modulation path 220, and then thesignal is filtered by the filter 222. In the calibration mode, the DAC221 transforms the calibration signal S_(D1) and the filter 222 filtersthe transformed calibration signal to generate the output voltage V_(L).In the normal mode, the DAC 221 transforms the amplitude signal and thefilter 222 filters the transformed amplitude signal.

Referring to FIG. 2, in one embodiment, the transmitter 200 can haveswitches SW1˜SW5. In the calibration mode, the switches SW1 and SW2switch to the calibration unit 240 such that the phase modulation path210 receives the calibration signal S_(D1) and the amplitude modulationpath 220 receives the calibration signal S_(D2). In this mode, theswitch SW3 switches to the detection module 232 such that the outputvoltage V_(L) is transmitted to the detection module 232. The SW4 isturned off and the SW5 is turned on such that the output voltage V_(t)is transmitted to the detection module 232.

In the normal mode, the switches SW1 and SW2 switch to the digitalmodulator 250 such that the phase modulation path 210 and the amplitudemodulation path 220 respectively receive the phase signal Φ(t) and theamplitude signal A(t). At this time, the switch SW3 switches to thecombiner 260. The SW4 is turned on and the SW5 is turned off. Thus, thecombiner 260 receives and combines the signals on the phase modulationpath 210 and the amplitude modulation path 220 to generate the RF signalS_(RF).

FIGS. 5˜7 are schematic diagrams of other exemplary embodiments of thetransmitter. FIGS. 5˜7 are similar to FIG. 1 except for the position ofthe delay module 231. Referring to FIG. 5, the delay module 231 iscoupled between the DAC 221 and the filter 222. Referring to FIG. 6, thedelay module 231 is coupled between the differentiator 2111 and thecompensation filter 2112. Referring to FIG. 7, the delay module 231 iscoupled between the process unit 211 and the fractional-N PLL 212.

FIG. 8 is a flowchart of an exemplary embodiment of a control method.The control method is utilized in a transmitter to transmit andcalibrate a phase signal and an amplitude signal. First, a phasemodulation path is provided to transmit the phase signal (step S810). Anamplitude modulation path is provided to transmit the amplitude signal(step S820). In a calibration mode, a calibration unit provides a firstcalibration signal and a second calibration signal to the phasemodulation path and the amplitude modulation path, respectively.

The signal on at least one of the phase modulation path and theamplitude modulation path is delayed (step S830). The signals on thephase modulation path and the amplitude modulation path may be delayedby the elements of the phase modulation path and the amplitudemodulation path. When the phase modulation path and the amplitudemodulation path respectively receive a first calibration signal and asecond calibration signal, the first calibration signal maybe slower orfaster than the second calibration signal. For example, if the secondcalibration signal is faster than the first calibration signal, thesecond calibration signal is delayed. Thus, the first and the secondcalibration signals are synchronous.

Since the signal on the amplitude modulation path is delayed, if a phasesignal is provided to the phase modulation path and an amplitude signalis provided to the amplitude modulation path, the phase signal and theamplitude signal are synchronous. In one embodiment, I/Q data ismodulated by a phase-amplitude modulator to separate out the phase andthe amplitude signals.

Referring to FIG. 2, the control unit 230 is utilized to determine whichsignal is faster. In the calibration mode, the detection module 232detects the difference of the first and the second calibration signalsand then generates an adjustment signal S_(ADJ) according to thedetection result. The delay module 231 delays at least one of the firstand the second calibration signals according to the adjustment signalS_(ADJ). In FIGS. 2 and 5, the delay module 231 delays the signal on theamplitude modulation path 220. In FIGS. 6 and 7, the delay module 231delays the signal on the phase modulation path 210.

When the first and the second calibration signals are synchronous, thedetection module 232 stops detecting the difference and maintains theadjustment signal S_(ADJ). Since the delay level of the detection module232 is maintained, the signals on the phase modulation path 210 and theamplitude modulation path 220 are synchronous.

Generally, when the phase modulation path or the amplitude modulationpath comprises a filter. Delay is easily introduced into the filter.Thus, in the calibration mode, the detection module 232 detects thefiltered signals. In one embodiment, the detection module 232 transformsthe filtered signals into differential pairs and then generates anadjustment signal S_(ADJ) according to the differential pairs.

Since the signals on the phase modulation path and the amplitudemodulation path may be delayed by the elements of the phase modulationpath and the amplitude modulation path, calibration signals are firstprovided to the phase modulation path and the amplitude modulation path.Then, the signals on the phase modulation path and the amplitudemodulation path are detected to determine which calibration signal isfaster. Then, the faster calibration signal is delayed by a delay modulesuch that the calibration signals on the phase modulation path and theamplitude modulation path are synchronous.

While the invention has been described by way of example and in terms ofthe preferred embodiments, it is to be understood that the invention isnot limited to the disclosed embodiments. To the contrary, it isintended to cover various modifications and similar arrangements (aswould be apparent to those skilled in the art). Therefore, the scope ofthe appended claims should be accorded the broadest interpretation so asto encompass all such modifications and similar arrangements.

1. A transmitter for transmitting and calibrating a phase signal and anamplitude signal, comprising: a phase modulation path for transmittingthe phase signal; an amplitude modulation path for transmitting theamplitude signal; a control unit delaying the signal on at least one ofthe phase modulation path and the amplitude modulation path; acalibration unit, wherein when the transmitter is in a calibration mode,the calibration unit is arranged to provide a calibration signal to theamplitude modulation path to serve as the amplitude signal; and adigital modulator, wherein when the transmitter is in a normal mode, thedigital modulator is arranged to provide the phase signal and theamplitude signal to the phase modulation path and the amplitudemodulation path, respectively.
 2. The transmitter as claimed in claim 1,wherein when the transmitter is in the calibration mode, the calibrationunit is arranged to provide the calibration signal to the phasemodulation path to serve as the phase signal.
 3. The transmitter asclaimed in claim 1, further comprising a combiner, wherein in the normalmode, the combiner combines the phase signal and the amplitude signal togenerate a radio frequency (RF) signal.
 4. The transmitter as claimed inclaim 1, wherein the control unit comprises: a detection modulegenerating an adjustment signal according to a difference between thephase signal and the amplitude signal transmitted in the calibrationmode; and a delay module delaying the signal on at least one of thephase modulation path and the amplitude modulation path according to theadjustment signal.
 5. The transmitter as claimed in claim 4, wherein thephase modulation path comprises a first filter for filtering the signalon the phase modulation path, the amplitude modulation path comprises asecond filter for filtering the signal on the amplitude modulation path,and the detection module transforms the filtered signals and generatesthe adjustment signal according to the transformed results.
 6. Thetransmitter as claimed in claim 5, wherein the detection modulecomprises: a first differential generator transforming the output offirst filter to generate a first differential pair; a seconddifferential generator transforming the output of second filter togenerate a second differential pair; a first comparator comparing thefirst differential pair; a second comparator comparing the seconddifferential pair; and a flip-flop generating the adjustment signalaccording to the compared results.
 7. The transmitter as claimed inclaim 5, wherein the detection module comprises: a first voltagegenerator receiving the output of first filter to generate a firstdivided signal; a second voltage generator receiving the output ofsecond filter to generate a second divided signal; a first comparatorcomparing the output of first filter and the first divided signal; asecond comparator comparing the output of second filter and the seconddivided signal; and a flip-flop generating the adjustment signalaccording to the compared results.
 8. The transmitter as claimed inclaim 4, wherein the phase modulation path comprises: a process unitprocessing the signal on the phase modulation path and outputting aprocessed result; and a fractional-N PLL transforming the processedresult.
 9. The transmitter as claimed in claim 8, wherein the processunit comprises: a differentiator differentiating the phase signal in thenormal mode; and a compensation filter increasing a high frequencycomponent of the first calibration signal in the calibration mode, andincreasing a high frequency component of the differentiated phase signalin the normal mode.
 10. The transmitter as claimed in claim 8, whereinthe fractional-N PLL comprises: a sigma-delta modulator (SDM) modulatingthe processed result to generate a modulated signal; and a phase-lockedloop (PLL) executing a phase locked procedure according to the modulatedsignal.
 11. The transmitter as claimed in claim 10, wherein the delaymodule is coupled between the process unit and the fractional-N PLL. 12.The transmitter as claimed in claim 9, wherein the delay module iscoupled between the differentiator and the compensation filter.
 13. Thetransmitter as claimed in claim 5, wherein the amplitude modulation pathfurther comprises a digital-to-analog converter (DAC) for transformingthe signal on the amplitude modulation path and the second filterfilters the transformed result.
 14. The transmitter as claimed in claim13, wherein the delay module is coupled between the DAC and the secondfilter.
 15. A control method for transmitting and calibrating a phasesignal and an amplitude signal, comprising: providing a phase modulationpath for transmitting the phase signal; providing an amplitudemodulation path for transmitting the amplitude signal; and delaying thesignal on at least one of the phase modulation path and the amplitudemodulation path, wherein in a calibration mode, a first calibrationsignal serves as the amplitude signal and in a normal mode, the phasesignal and the amplitude signal are provided by a digital modulator tothe phase modulation path and the amplitude modulation path.
 16. Thecontrol method as claimed in claim 15, wherein in the calibration mode,the calibration signal serves as the phase signal.
 17. The controlmethod as claimed in claim 15, wherein the step of the delayingcomprises: detecting the difference between the phase signal and theamplitude signal transmitted in the calibration mode; and delaying thesignal on at least one of the phase modulation path and the amplitudemodulation path according to the detection result.
 18. The controlmethod as claimed in claim 17, wherein in the normal mode, detection ofthe difference between the signals on the phase modulation path and theamplitude modulation path is stopped.
 19. The control method as claimedin claim 17, further comprising: filtering the signals on the phasemodulation path and the amplitude modulation path for generating a firstfiltered signal and a second filtered signal; detecting the differencebetween the first and the second filtered signals for generating anadjustment signal; and delaying the signal on at least one of the phasemodulation path and the amplitude modulation path according to theadjustment signal.
 20. The control method as claimed in claim 19,further comprising: transforming the first and the second filteredsignals into a first differential pair and a second differential pair;and delaying the signal on at least one of the phase modulation path andthe amplitude modulation path according to the first and the seconddifferential pairs.
 21. A transmitter for transmitting and calibrating aphase signal and an amplitude signal, comprising: a first filtergenerating the phase signal according to a first signal; a second filtergenerating the amplitude signal according to a second signal; a controlunit delaying at least one of the first and the second signals; acalibration unit providing a calibration signal to serve as the secondsignal in a calibration mode; and a digital modulator generating a firstmodulated data and a second modulated data, wherein the first modulateddata is served as the first signal and the second modulated data isserved as the second signal in a normal mode.